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Map: Near 99th Ave. & Peoria

PEORIA, Ariz. -- Police and fire investigators confirm that an overnight fire at a Peoria strip mall was arson and say three gas cans found at the scene are being treated as evidence.

The fire was reported shortly after 11 p.m. Tuesday just north of 99th and Peoria avenues, and it took about two dozen units from six cities to knock it down.

Because the building is old, it was not equipped with sprinklers. Without that water to contain them, the flames spread quickly through the shared attic space.

CCIC Beauty College, which is where the fire started, was gutted and businesses on either side, including New Life Worship Center, Custom Fit Swimwear/Bras and a nail salon, sustained heavy smoke damage.

Six firefighters were pulled out of the building when ceiling tiles started to fall, which is an indication that the roof is about to collapse. That's exactly what happened moments after the firefighters made it outside.

No injuries were reported, but investigators quickly classified this fire as suspicious. They confirmed it was arson several hours later.

Three gas canisters were left in the parking lot. Those cans are being treated as evidence in the case.

Fire and crime-scene investigators returned to the scene shortly after 6:30 a.m. Wednesday. An accelerant-sniffing dog from Avondale and ATF agents will be there later in the day.